1. Field of the Invention
The invention relates to xe2x80x9cone-wayxe2x80x9d clutches wherein the clutch is selectively disabled to permit xe2x80x9cfree-wheelingxe2x80x9d of the driven member in either rotational direction relative to the driving member.
2. Background Information
Clutches are used in a wide variety of applications to selectively couple power from a first rotatable xe2x80x9cdrivingxe2x80x9d member, such as a driving disk or plate, to a second, independently-rotatable xe2x80x9cdrivenxe2x80x9d member, such as a driven plate or disk. In one known variety of clutches, commonly referred to as xe2x80x9cone-wayxe2x80x9d or xe2x80x9coverrunningxe2x80x9d clutches, the clutch xe2x80x9cengagesxe2x80x9d to mechanically couple the driving member to the driven member only when the driving member seeks to rotate in a first direction relative to the driven member. Once so engaged, the clutch will release or decouple the driven member from the driving member only when the driving member rotates in a second, opposite direction relative to the driven member. Further, the clutch otherwise permits the driving member to freely rotate in the second direction relative to the driven member. Such xe2x80x9cfree-wheelingxe2x80x9d of the driving member in the second direction relative to the driven member is also known as the xe2x80x9coverrunningxe2x80x9d condition.
Occasionally, it is desirable to deploy a plurality of such one-way clutches along a common rotational axis in order to selectively drive a given output shaft in a selected rotational direction notwithstanding continuous rotation of an input shaft in a single rotational direction. For example, in a known embodiment, a driving member is disposed about a common rotational axis between a pair of driven members, with the driving member being axially translated relative to one or the other of the driven members to thereby permit exclusive torque transmission between the driving member and a selected one of the driven members using a one-way clutch. Because each driven member includes a plurality of circumferentially-spaced gear teeth to define a respective bevel gear, and because each bevel gear simultaneous meshes with a common pinion, the pinion is caused to be driven in opposite directions depending upon which driven member is mechanically coupled for rotation with the driving member. In this manner, an output shaft coupled to the pinion is selectively driven in either direction based upon the selected axial position of the driving member. A xe2x80x9cneutralxe2x80x9d position is advantageously provided by axially translation of the driving member to a position intermediate the two driven members, whereby rotation of the driving member does not produce any rotary output. Unfortunately, the need to axially translate the driving member relative to the driven members (or, indeed, each of several coaxial clutch assemblies deployed along a common drive shaft) and the resultant actuating structures implicates greater levels of mechanical complexity and increases the overall size of each such clutch assembly.
It is an object of the invention to provide a clutch assembly with which to selectively couple an input shaft to an output shaft to thereby generate a rotary output in a selected rotational direction, which overcomes the deficiencies of the prior art.
Under the invention, a clutch assembly includes a driving member that is selectively and controllably rotatable about a first axis in each of two opposite rotational directions, for example, by an electric motor in accordance with a preferred method described further below. The driving member includes a first driving face that preferably defines a first reference surface that is generally perpendicular to the first axis. In a preferred embodiment, the driving member further includes a second driving face on the opposite side of the driving member that likewise preferably defines a second reference surface that is generally perpendicular to the first axis. The driving faces of the driving member each include at least one recess, with each recess defining a load-bearing shoulder that is operative when the driving member is rotated in the first direction, and with each recess preferably being adapted to receive a strut in the manner described further below. Significantly, each recess defined on the first driving face of the first driving is angularly offset from, i.e., is not axially aligned with, any recess defined on the driving member""s second driving face.
The clutch assembly of the invention also includes a first driven member, also rotatable about the first axis, that includes a driven face in close-spaced opposition with the first driving face of the driving member and, hence, in the preferred embodiment, likewise defines a respective reference surface that is generally perpendicular to the first axis. The driven face of the first driven member includes a plurality of recesses, with each recess defining a respective load-bearing shoulder. A first coupling is disposed between the first driving face of the driving member and the driven face of the first driven member. The first coupling includes a first strut that, in a preferred embodiment, is carried by the driving member so as to rotate with the driving member. The first strut is moveable between a first position characterized by simultaneous abutting engagement of a respective end of the first strut with a respective shoulder of both the first driving face of the driving member and the driven face of the first driven member, and a second position characterized by non-engagement of the first strut with at least one of the first driving face of the driving member and the driven face of the first driven member (in the preferred embodiment, wherein the first strut is carried by the driving member within the recess defined in the driving member""s first driving face, the second position is characterized by the nonengagement of the first strut with the driven face of the first driven member).
The first coupling also includes a first spring, for example, carried by the driving member, that urges the first strut toward the first position; and a first strut retainer rotatable about the first axis that operates to urge the first strut to the second position when the first strut retainer is rotated into a first predetermined rotational position relative to the driving member. By controlling the rotational position of the first strut retainer relative to the driving member, the first strut retainer is used to selectively enable or disable the nominal operation of the one-way planar clutch that is otherwise defined by the opposed members and the first coupling""s spring-biased strut.
Critically, under the invention, the first strut retainer is rotatable about the first axis so as to rotate with the driving member only when the driving member is rotated in the first rotational direction relative to the first driven member, and, further, to rotate with the first driven member only when the driving member rotates in the second rotational direction relative to the first driven member. In this manner, the first strut is urged by the first strut retainer into the second, non-engaging position by controllably rotating the driving member in the second rotational direction into the first predetermined rotational position, whereupon the first one-way clutch defined by the driving member, the first driven member, and elements of the first coupling is disabled, with the driving member thereafter being free to xe2x80x9cfree-wheelxe2x80x9d in the first rotational direction. It will be appreciated that, upon subsequent further rotation of the driving member in the second rotational direction relative to the driven member, the first strut retainer will rotate with the driving member out of the first predetermined rotational position, whereupon the thus-defined first one-way clutch is enabled to transmit power from the driving member to the first driven member upon subsequent relative rotation of the driving member in the first rotational direction and to xe2x80x9cfree-wheelxe2x80x9d when the first driven member overruns the driving member while rotating in the first rotational direction.
As noted above, in a preferred embodiment, the clutch assembly further includes a second driven member rotatable about the first axis. The second driven member includes a driven face that is in close-spaced opposition with the second driving face of the driving member and, in the preferred embodiment, likewise defines a respective reference surface that is generally perpendicular to the first axis. The driven face of the second driven member includes a plurality of recesses, with each recess defining a respective load-bearing shoulder. A second coupling is likewise disposed between the second driving face of the driving member and the driven face of the second driven member.
As in the first coupling, the second coupling includes a second strut that is preferably carried by the driving member on its second driving face so as to rotate with the driving member. The second strut is likewise moveable between a first position characterized by simultaneous abutting engagement of a respective end of the second strut with a respective shoulder of both the second driving face of the driving member and the driven face of the second driven member, and a second position characterized by non-engagement of the second strut with at least one of the second driving face of the driving member and the driven face of the second driven member. The second coupling also includes a second spring urging the second strut toward the first position, as well as a second strut retainer that is rotatable about the first axis and that urges the second strut to the second position when the second strut retainer is rotated into a second predetermined rotational position relative to the driving member.
Once again, under the invention, by controlling the rotational position of the second strut retainer relative to the driving member, the second strut retainer is used to selectively enable or disable the nominal operation of the one-way planar clutch that is otherwise defined by the opposed members and the second coupling""s spring-biased strut. As with the first strut retainer, the second strut retainer is rotatable about the first axis so as to rotate with the driving member only when the driving member is rotated in the first rotational direction relative to the second driven member, and, further, to rotate with the second driven member only when the driving member rotates in the second rotational direction relative to the first driven member. In this manner, the second strut is urged by the second strut retainer into the second, non-engaging position by controllably rotating the driving member into the second rotational direction into the second predetermined rotational position, whereupon the second one-way clutch defined by the driving member, the second driven member, and elements of the second coupling is disabled, with the driving member thereafter being free to xe2x80x9cfree-wheelxe2x80x9d in the first rotational direction. It will be appreciated that, upon subsequent further rotation of the driving member in the second rotational direction relative to the driven member, the second strut retainer will rotate with the driving member out of the first predetermined rotational position, whereupon the thus-defined first one-way clutch is enabled to transmit power from the driving member to the first driven member upon subsequent relative rotation of the driving member in the first rotational direction and to xe2x80x9cfree-wheelxe2x80x9d when the first driven member overruns the driving member while rotating in the first rotational direction.
In the preferred embodiment, the first and second driven members respectively include a plurality of circumferentially-spaced gear teeth defined on a radially-outward surface portion, for example, to thereby respectively define a bevel gear. Each bevel gear is positioned for simultaneous meshing engagement with a common pinion such that rotary power transmitted between the driven members through the pinion causes the driven members to rotate in opposite rotational directions. In this manner, the pinion is driven by a selected one of the driven members while the other of the driven members xe2x80x9cfree-wheelsxe2x80x9d by virtue of its respective, xe2x80x9cdisabledxe2x80x9d one-way clutch, with the selected driven member dictating the direction in which the pinion rotates as the driving member is otherwise rotated in the first rotational direction.
In accordance with another feature of the invention, in a preferred embodiment, the first and second predetermined rotational positions are defined by the respective relative angular position of the recess defined in the respective first and second driving faces of the driving member. It will be appreciated that, where the clutch assembly employs a plurality of recesses on each of the driving member""s driving faces, there will be a like number of xe2x80x9cfirst and second rotational positionsxe2x80x9d for the strut retainers in which the strut retainers operate to xe2x80x9cdisablexe2x80x9d the respective one-way clutches. In a preferred embodiment, the clutch assembly further includes a sensor, such as a Hall-effect sensor, which is advantageously used to detect the relative rotational position of the driving member for use in selectively operating the first and second one-way clutches of the preferred embodiment.
While an exemplary clutch assembly in accordance with the invention is illustrated and disclosed, such disclosure should not be construed to limit the claims. It is anticipated that various modifications and alternative designs may be made without departing from the scope of the invention.